Abstract: This paper presents a new method using the damage induction vector (DIV) and the best vector (BV) by which the change of modes due to structural damage can be employed to determine the location and scale of damage in structures, Using DIV, undamage elements can be easily identified and the damage identification can be focused on a few domains of the structure,The smictural damages are located by computing the Euclidean distance between the DIV and its BV, The loss of both stickness and mass properties can be quantified, The characters of thismethod are less calculation and no limitation of damage scale, Finally, the effectiveness of the method is demonstrated by detecting the damages of shallow arches.